alsamrob

If I only fold one, will I go in a circle?

MadFox

Actually, this has been discussed before (search "terminal velocity"), it resulted in the following post since the engineer in me wanted to really know how fast one could get your Cayenne in a "descent"! Original post 4/27/06
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TOPIC: 674 MPH Cayenne S (Turbo still faster @ 690 MPH)
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.....The 200MPH thread got me thinking when WINGLESS made the "dump it out of a plane" speed comment... with a drag co-efficient of .39 we can calculate the actual rate at what our beloved Cayenne would actually "fly" into the earth.

Terminal velocity: An object which is falling through the atmosphere is subjected to two external forces. One force is the gravitational force, expressed as the weight of the object. The other force is the air resistance, or drag of the object. The motion of any object can be described by Newton's second law of motion, force F equals mass m times acceleration a: F = m * a which can be solved for the acceleration of the object in terms of the net external force and the mass of the object: a = F / m. Weight and drag are forces which are vector quantities. The net external force F is then equal to the difference of the weight W and the drag D: F = W - D. The acceleration of a falling object then becomes: a = (W - D) / m . The magnitude of the drag is given by the drag equation. Drag D depends on a drag coefficient Cd, the atmospheric density r, the square of the air velocity V, and some reference area A of the object: D = Cd * r * V ^2 * A / 2

Drag increases with the square of the speed. So as an object falls, we quickly reach conditions where the drag becomes equal to the weight, if the weight is small. When drag is equal to weight, there is no net external force on the object and the vertical acceleration goes to zero. With no acceleration, the object falls at a constant velocity as described by Newton's first law of motion. The constant vertical velocity is called the terminal velocity. Using algebra, we can determine the value of the terminal velocity. At terminal velocity: D = W

Cd * r * V ^2 * A / 2 = W

Solving for the vertical velocity V, we obtain the equation

V = sqrt ( (2 * W) / (Cd * r * A)

Thus, let's assume NO ONE is inside the vehicle and the only "luggage" is ltc's former straight jacket and/or his TCU! The calculation for a S would be if we shoved it out of a cargo plane at 35,000 feet:

V= sqrt ((2*4949 lbs.)/(.39 * air density (fm table) * Area (front view ~ 75.9" x 66.9") A= 35.2 sq.ft.

THUS -- Actual Maximum speed of a Cayenne S is 674.1 MPH! or 988.7 ft/sec.
A Turbo is still slightly faster than a S!! 690.5 MPH or 1012.7 ft/sec

tommytomaso

And all these years i thought that terminal velocity of most objects in our gravity was around 127mph...
or are we figuring that said "flying pig" is racing down a near vertical hill and foward traction is driving the "pig" toward the speed of sound using HP and gravity alone?......just think what speed you could get with "MOON" dish wheel covers ,no mirrors, roof rack and no entenia....man it would move so fast when it hit the ground it would just go "PLUNK" right into the sand...like a superfast streamlined rock into water. hehehhehe

MadFox

.... the possiblities on how to "improve" a Cayenne's airborne demise are endless!

With that said, and only again, because I was curious.. Tommy, you're pretty close to what a normal free fall skydiver is falling --- but sadly, a few jetliners have proven that the speed is much much higher for something aerodynamic and pointed straight down. Here's also some amazing numbers on humans:

"Based on wind resistance, for example, the terminal velocity of a skydiver in a free-fall position with a semi-closed parachute is about 195 km/h (120 mph or 55 m/s). Higher speeds can be attained if the skydiver pulls in his limbs (see also freeflying). In this case, the terminal velocity increases to about 320 km/h (200 mph or 90 m/s),which is also the terminal velocity of the peregrine falcon diving down on its prey.And the same terminal velocity is reached for a typical 150 grain bullet travelling in the downward vertical direction — when it is returning to earth having been fired upwards, or perhaps just dropped from a tower — according to a 1920 U.S. Army Ordinance study.

Competition speed skydivers fly in the head down position reaching even higher speeds. The current world record is 614 mph (988 km/h) by Joseph Kittinger, set at high altitude where the lesser density of the atmosphere decreased drag."

tommytomaso

WOW...all i have to say is WOW!...he is the fastest human....wounder how bad his wind burn was...lol

sigs

MadFox, this reminds me of a joke that we used to tell on each other in college - That it wasn't true that we actually PREFERRED doing our physics problem sets to having sex, but it WAS true that we would THINK about our physics problem sets DURING sex, thus making sex all the more enjoyable.

Just to bring this back to the OP's question, I've tracked my CTT-PK mulitple times in the past, and I only bought it after using the PDE in Birmingham as an extended test drive. It is impressive - for an SUV. You can find extensive debates on this topic if you search this forum. As for top end, mine pulls easily to 140 (given speedo error) and feels like its got plenty left, but I've never driven it anywhere I could safely exceed that. At about 125, you gain a new appreciation for all the old threads about tire balancing and road force issues.

CTurbo77

< cough cough >




My Pig loves the track..... these were at Motorsports Park Hastings in Nebraska





My CTT beat virtually all the "proper" sports cars around the track, including a twin turbo'd 350Z , modded 911 C2, modded Boxster ...etc etc

Got spanked by the ZO6 and GTR

Renn 951

I think I'd recommend both hands on the wheel at that speed - 9 and 3 o'clock...

medtech

Yes, but If he had both hands on the wheel, he wouldn't be able to take the picture!

alex911s

lolol


I dont drive fast anymore,, i tried 150 on my ctt, but i forgot which one

Reborn996

Hmmm.... I have done 130 on the 11th street onramp to 205 Westbound numerous times. Maybe 1.5 miles long if that.

alex911s

isnt it only 55mph there?

CTurbo77

Now that would be quite a feat.......taking pictures from the passenger side while driving at 150mph!!


Thankfully, my co-pilot was able to document my speed during our trip.....


both hands are on the wheel, at the very bottom of the wheel..... just goes to show how rock solid these "pigs" are at high speeds

jplondon

120 on I90 briefly didnt take much effort...